Such methods are used, for instance, to operate a variable-speed drive for moving a movable element such as a window pane, a sliding roof, a seat, etc., of a vehicle. The element is movable along a predefined path of motion between two block positions. Each block position is formed as a limit stop. The drive includes an electric motor configured to drive the element with motor power in order to move the element along the path between and into the block positions.
As an example, the element is a window pane of a vehicle. The window pane is movable relative to a window frame of the vehicle along a predefined path of motion between two block positions. One of the block positions (i.e., the upper block position) defines the closed position of the window pane. The other block position (i.e., the lower block position) defines the opened position of the window pane. As such, each block position is a limit stop in that each block position defines respective end points of the path of motion. Further, any position of the window pane along the path between the closed and opened positions is an intermediate position of the window pane along the path.
A window-lifter drive having an electric motor is associated with the window pane. The drive is configured to drive the window pane with power from the motor in order to move the window pane along the path of motion. The drive is further configured to operate the motor to carry out a braking action of the motion of the window pane as the window pane is moved into either block position. The drive operates the motor to cause the braking action to be more pronounced in the case of the window pane moving into the lower block position that characterizes the opened position of the window pane. The drive operates the motor to provide the braking action in order to bring the window pane as smoothly as possible into a block position (i.e., a limit stop). The braking action prevents the window pane from bouncing back from a block position upon moving into the block position. The braking action also reduces spring-back of the mechanical force transmission between the window pane and the motor and reduces annoying impact noises that could lead a user to suspect a defect in the drive.
DE 196 18 484 A1 (corresponding to U.S. Pat. No. 6,194,855) describes a method for moving a window pane with power of a motor of a drive associated with the window pane. The method includes reducing the motor power to a minimal power level in order to decelerate the window pane as the window pane is approaching a block position. The motor power is gradually reduced to the minimal power level starting at a predetermined intermediate position of the window pane along the path of motion away from a block position. The window pane is then retracted (i.e., moved) into the block position with the minimal remaining power of the motor. Due to the presence of a window seal on the upper-side of the window frame, such a procedure is generally not provided during retraction of the window pane into the upper block position as the seal causes a deceleration of the motion of the window pane during the closing process of the window pane.
Both during an application of this method for retracting the window pane into the lower blocked position as well as by the retraction that decelerates the entry of the window pane into the window seal in the upper block position, bursts of noise that may be experienced as disturbing from the user side could occur. Moreover, the deceleration process in the first case of the opening process of the window pane requires a time interval that is relatively long such that the braking action of the window pane is perceivable by a user.